Corrosion resistant aluminum alloy



Patented Oct. 31, 1933 CORROSION RESISTANT ALUMINUM ALLOY William E. McCullough, Detroit, Mich, assignor to Bohn Aluminum & Brass Corporation, Detroit, Mich, a corporation of Michigan No Drawing. Application May 22, 1933 Serial No. 672,353

1 Claim.

The invention relates to aluminum alloys and has for its object the obtaining of a material particularly adapted for use in forming architectural moldings which are exposed to the action of the weather. For such uses it is desirable, first, that the material should be corrosion resistant so as to retain its brightness and luster; second, that it should have sufficient physical strength to maintain its form both during the process of erection and under any stresses to which it may subsequently be exposed.

Heretofore aluminum alloys have been obtained which are highly resistant to corrosion but which are lacking in physical strength. For

instance, an alloy containing relatively small amounts of oxide free copper, such as boronized copper, silicon, cobalt and chromium, will be corrosion resistant, but will have only slightly greater strength than virgin aluminum. I have discovered that the physical properties of such material may be greatly improved by the additlon of a small amount of magnesium. Such an alloy is harder than that where the magnesium element is omitted, but it is nevertheless suitable for extrusion. By subsequent heat treatment the physical properties are further improved.

My improved alloy is of the following composition:

Balance mainly of commercial aluminum.

A specific example of the above is the following: 1

Per cent Copper- .25

Iron .57 0 Silicon .94 Cobalt .30 Chromium .73 Magnesium .51

Balance of commercial aluminum. 5

A billet of this alloy when extruded under a temperature of 930 F. through a 1 x 1 two-hole die and subsequently heat treated, shows the following characteristics:

. B.H.N. Condition g 332 332 5; 5012153.. 10

As extrudcd- 15,730 27, 21.5 as 5111's. 915 F.,alr cool 19,200 37,400 21.5 76 5hrs. 975 F., quench.. 42,600 50, 18.0 114 10 hrs. 350 F., draw" It will be noted from the above table that the physical properties are greatly improved by heat 80 treatment with air cooling, but are still further improved where after heat treatment the material is quenched and then drawn.

What I claim as my invention is:

An aluminum alloy comprising Per cent Copper .05 Chromium .75 to 1.5 Cobalt .25 to .5 Silicon .75 .to 3 9o Magnesium .5 to 1.25 Balance commercial aluminum.

W E. MCCULLOUGH. 

